There has been proposed a case with a cover, for containing cosmetics or the like therein, in which a torsion bar is disposed at a hinge in an opening/closing mechanism, a resilient force is reserved by a twist applied to the torsion bar by a cover closing operation, and the cover is automatically opened by utilizing the release of the resilient force (see Patent Literature 1).
The case of this type adopts a structure in which grease is kept to be charged around the torsion bar, and therefore, since the grease charged around the torsion bar resists against (or interferes with) the release of the twist of the torsion bar when the cover is opened, the cover is slowly opened.
Besides the torsion bar, there has been known a case with a cover that is of the type opened by urging force of an urging member (see Patent Literature 2).
In such a case, a fixed side member and a turn side member are disposed at a case body and the cover, respectively. Blades are disposed at a tip of the fixed side member: in the meantime, gel is charged with the turn side member. Thus, the fixed side member is configured in such a manner as to be inserted into the turn side member. As a consequence, the blades agitate the gel to resist against (or interfere with) the gel when the cover is opened, so that the cover is slowly opened in the same manner.    Patent Literature 1: Japanese Laid-Open Patent Publication No. H5-84115    Patent Literature 2: Japanese Laid-Open Patent Publication No. H6-48517